Mentor Graphics Corporation

Other

Christophe Gauthron

Jeremy Rutledge Levitt

Chian-Min Richard Ho

Ping Fai Yeung

Kalyana C Mulam

Ramesh Sathianathan

James Andrew Garrard Seawright

The amount of analysis performed in determining the validity of a property of a digital circuit is measured concurrent with performance of the analysis, and provided as an output when a true/false answer cannot be provided e.g. when stopped due to resource constraints. In some embodiments, a measure of value N indicates that a given property that is being checked will not be violated within a distance N from an initial state from which the analysis started. Therefore, in such embodiments, a measure of value N indicates that the analysis has implicitly or explicitly covered every possible excursion of length N from the initial state, and formally proved that no counter-example is possible within this length N.

Measure of analysis performed in property checking

An edge clock model is used to capture states from a logic-level simulation of a circuit description. The states are captured at clock edges, or transitions, according to an edge clock model based on a clock specification for the circuit description. The captured states and associated attributes are used in formal verification of the circuit description. This approach helps to reduce or eliminate inaccuracies and other issues with other clock models such as a phase clock model. In one embodiment, a phase clock model can be used in addition to the edge clock model. In another embodiment, the edge clock states can be used to generate states according to different clock models, such as the phase clock model.

Clock model for formal verification of a digital circuit description

A computer is programmed to automatically select a state or a set of states of a digital circuit that are visited during simulation, for use as one or more initial states by a formal verification tool. Such automatic selection of one or more simulation states reduces the set of all simulation states to a small subset, thereby to address the state space explosion problem. Depending on the embodiment, the programmed computer uses one or more criteria provided by a library and/or by the user, in making its selection of states. Such criteria may be based on a property (assertion/checker) of the digital circuit and/or a signal generated during simulation. Furthermore, after such criteria (also called 'primary criteria') are applied, the selected states may be pruned by application of additional criteria (also called 'secondary criteria') prior to formal analysis.

Selection of initial states for formal verification

The amount of analysis performed in determining the validity of a property of a digital circuit is measured concurrent with performance of the analysis, and provided as an output when a true/false answer cannot be provided e.g. when stopped due to resource constraints. In some embodiments, a measure of value N indicates that a given property that is being checked will not be violated within a distance N from an initial state from which the analysis started. Therefore, in such embodiments, a measure of value N indicated that the analysis has implicitly or explicitly covered every possible excursion of length N from the initial state, and formally proved that no counter-example is possible within this length N.

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Mountain View, CA, United States of America

Christophe Gauthron